1561217205 has 16 divisors (see below), whose sum is σ = 2521295424. Its totient is φ = 824866560.

The previous prime is 1561217149. The next prime is 1561217227. The reversal of 1561217205 is 5027121651.

It is not a de Polignac number, because 1561217205 - 2⁹ = 1561216693 is a prime.

It is a super-2 number, since 2×1561217205² = 4874798322376024050, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 484756 + ... + 487965.

It is an arithmetic number, because the mean of its divisors is an integer number (157580964).

Almost surely, 2^1561217205 is an apocalyptic number.

1561217205 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1561217205 is a deficient number, since it is larger than the sum of its proper divisors (960078219).

1561217205 is a wasteful number, since it uses less digits than its factorization.

1561217205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 972836.

The product of its (nonzero) digits is 4200, while the sum is 30.

The square root of 1561217205 is about 39512.2412044673. The cubic root of 1561217205 is about 1160.0795637559.

Adding to 1561217205 its reverse (5027121651), we get a palindrome (6588338856).

The spelling of 1561217205 in words is "one billion, five hundred sixty-one million, two hundred seventeen thousand, two hundred five".